Shoreline position (1D) and coastal topographical (2D) change monitoring at Gateway National Recreation Area: 2012-2017 trend report

Psuty, Norbert; Butler, Kelly; Ames, Katherine; Habeck, Andrea

The Trend Report summarizes the results of shoreline position and coastal topography surveys conducted from Spring 2012 through Spring 2017 at sites within Gateway National Recreation Area. Gateway National Recreation Area is made up of three units: Sandy Hook Unit, Jamaica Bay Unit (Breezy Point, Plumb Beach), and Staten Island Unit (Great Kills, Miller Field, Fort Wadsworth). Shoreline data sets include a spatial depiction and statistical data of annual changes and 5-year changes in shoreline position as well as a longer-term trend analysis incorporating the full shoreline dataset, all following the model presented in Psuty et al. (2010b). Coastal topography datasets include profiles of survey data collected annually, annual change metrics, net change metrics, as well as an alongshore depiction of net change, following the model presented in Psuty et al. (2012). This 2012 to 2017 Trend Report is the first Gateway National Recreation Area Trend Report to incorporate both shoreline and coastal topographical change data. Due to the variable exposure to incident waves influencing inputs of sediment to the alongshore transport system in the various units from updrift sources, there was no common direction of shoreline displacement or profile change throughout the Gateway National Recreation Area Parks. Engineering structures along the beach and adjacent to inlets altered the shoreline position and coastal topography responses in much of Gateway National Recreation Area. Generally, the largest vectors of shoreline change and changes in coastal topography were produced by natural impacts such as storms (e.g., Hurricane Sandy and subsequent winter storms) and by anthropogenic impacts such as beach nourishment or dredging. All shorelines and coastal topography profiles surveyed during the 2012 to 2017 period were eroded by Hurricane Sandy (October 2012). Sites with ocean exposure were more heavily eroded (Sandy Hook Oceanside, Breezy Point Oceanside, and Great Kills Oceanside), than sheltered sites (Sandy Hook Bayside, Breezy Point Bayside, Great Kills Bayside, Miller Field, Fort Wadsworth). The Sandy Hook and Great Kills Oceanside shorelines never fully recovered from the landward displacement caused by Hurricane Sandy and the shorelines continued to be displaced landward in the post-storm period. Persistent erosion post-storm also occurred in the coastal topography profiles along the bayside of Sandy Hook and Breezy Point. Beach nourishment efforts updrift affected post-storm recovery at Sandy Hook, Plumb Beach and Breezy Point by adding sediment into the system. Breezy Point Oceanside was the only site with a positive trend in shoreline and beach cross-section area gain over the report period. Erosion downdrift of structures at Plumb Beach and Great Kills Oceanside potentially threaten infrastructure located inland. Throughout the survey period there was consistent landward displacement of the shoreline and cross-section area loss downdrift of the eastern groin at Plumb Beach and of the bluff area at Great Kills. Consistent monitoring provides information for management, and trend analysis can help management anticipate and adjust to potential impacts. In a comparison of shoreline change in this Trend Report with rates from the previous Trend Report, all shorelines within GATE except for Breezy Point Oceanside and Great Kills oceanside were more negative in this recent period. Due to Hurricane Sandy and lack of recovery post-storm, Sandy Hook, Breezy Point Bayside, Plumb Beach, Great Kills Oceanside, Miller Field and Fort Wadsworth all had greater rates of landward shoreline displacement than during the previous period. Breezy Point Oceanside had a more positive shoreline displacement rate from 2012 to 2017 due to the large beach nourishment project in 2014. Great Kills Bayside had a similar seaward displacement rate in both trend reporting periods.

Shoreline position (1D) and coastal topographical (2D) change monitoring at Gateway National Recreation Area: 2012-2017 trend report

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